1. In modern electronics, differential signals are often used to improve signal fidelity (signal to noise ratio). Differential signaling is used in a variety of settings, including:                high speed digital circuits        analog/radio frequency circuits        high speed computation and communications equipment        high voltage circuits        
For computation and communications equipment, differential signaling (e.g., using a serializer/deserializer) is used to address a clock skew issue. In analog and radio frequency equipment, differential signaling reduces sensitivity to electromagnetic interference. For high voltage circuits, differential signaling can be used because both transmission mechanisms can be electrically floated, and control signals or analog signals can be provided independent of the DC offset voltage.
Differential signaling has costs too, and does not work perfectly in practice. For example, a single mode of signal propagation is typically desirable for electromagnetic signals, as multi-mode signal propagation may result in non-idealities due to coupling (interference) between signal components of the different modes. The desirable single mode may be referred to as the differential mode, an odd mode, a first mode and so on, and undesirable modes may be referred to as a common mode, an even mode, a higher order mode, a second mode, a third mode, a fourth mode and so on.
Selective filters have been used to suppress the undesirable (common, even, higher order, second/third/fourth) mode signals on differential transmission assemblies. The differential transmission assemblies are loaded with stopband filters for the undesirable mode signals and all-pass filters for the desirable mode signals.